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Bone Densitometry. Interpretation of DEXA. Osteoporosis.

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bone densitometry

Bone Densitometry

Interpretation of DEXA

osteoporosis
Osteoporosis
  • Osteoporosis is the most common metabolic bone disorder. It has been defined by the National Institutes of Health as an age-related disorder characterized by decreased bone mass and increased susceptibility to fractures in the absence of other recognizable causes of bone loss.
osteoporosis1
Osteoporosis
  • Risk factors
    • may be superimposed upon either involutional or secondary osteoporosis, including :
  • Smoking
  • Alcohol
  • Poor diet
  • Lack of exercise
  • An early menopause
  • Strong family history
  • Small frame
osteoporosis2
Osteoporosis
  • The normal rate of bone loss is 2% per year, hence 20-40% of the female bone mass is already lost by the age of 65 years of age, beginning before the menopause and accelerating afterwards
osteoporosis3
Osteoporosis

Osteoporosis progression over 2Y UC Steroids 59F

osteoporosis4
Osteoporosis
  • Bone mass is the major determinant of bone strength that can be measured by non-invasive techniques, and accounts for 75-85% of this parameter
osteoporosis measurement
Osteoporosis Measurement
  • Plain film,
    • Subjective, Radiogrammetry, Osteogram
  • SPA
  • DPA
  • DEXA
  • QCT
  • US
  • MRI
osteoporosis measurement1
Osteoporosis Measurement
  • Plain film,
    • Subjective, Radiogrammetry, Osteogram
  • SPA
  • DPA
  • DEXA
  • QCT
  • US
  • MRI
osteoporosis measurement2
Osteoporosis Measurement
  • Plain film,
    • Subjective, Radiogrammetry, Osteogram
  • SPA
  • DPA
  • DEXA
  • QCT
  • US
  • MRI
osteoporosis measurement3
Osteoporosis Measurement
  • Plain film,
    • Subjective, Radiogrammetry, Osteogram
  • SPA
  • DPA
  • DEXA
  • QCT
  • US
  • MRI
osteoporosis measurement4
Osteoporosis Measurement
  • Plain film,
    • Subjective, Radiogrammetry, Osteogram
  • SPA
  • DPA
  • DEXA
  • QCT
  • US
  • MRI
slide12
DEXA

DEXA has very high

accuracy

(the difference in the measurement from a known standard)

and

precision

(observed deviation of serial measurements with time)

both short and long term

to within 1% at the hip and spine

slide13
DEXA
  • DEXA is at present the most precise measurement of BMD
  • QCT is more sensitive to change
slide15
Find out as much

relevant information

as possible

slide16
Find out as much

relevant information

as possible

bone densitometry dexa spine check list
Bone DensitometryDEXA spine check list
  • Note the age, sex, ethnicity and weight
  • Does this match the reference ranges?
  • Is the bottom of L4 roughly at the level of the iliac crests
  • Are there any ribs on L1
  • Scoliosis
  • Are the vertebrae correctly divided
  • Anything in the soft tissue
bone densitometry dexa spine check list1
Bone DensitometryDEXA spine check list
  • Look for significant level to level variations
  • 15-20% difference between adjacent levels
bone densitometry1
Bone Densitometry
  • In preventing Fxs it is the worst scenario that matters.
  • Generally a slight increase in density as descend the L spine.
  • Approx 6% increase between L1 and L4.
what s wrong with this scan
What’s wrong with this scan?

Divisions don’t account for scoliosis

dexa femur check list hints for a good scan
DEXA Femur check listHints for a good scan.
  • Patient should be straight on table.
  • Pack patient with rice bags.
  • Shaft of femur should be straight.
  • Rotate leg inward, this will hide the lesser trochanter.
dexa femur check list hints for a good scan1
DEXA Femur check listHints for a good scan.
  • The Wards area is roughly half the neck area
  • Trochanteric area 8-14cm2 in women, 10-16cm2 in men
  • Check left and right and state side being used in report.
what s wrong with this scan3
What’s wrong with this scan?

Insufficient tissue below neck

what s wrong with this scan4
What’s wrong with this scan?

Set up for wrong leg

bone densitometry who uses t scores
Bone DensitometryWHO uses T scores
  • Normal
    • > -1 SD below young adult
  • Osteopenia
    • -1 -2.5 SD
  • Osteoporosis
    • <-2.5 SD
  • Established (Manifest) Osteoporosis
    • + Fxs, usually spine, hip, proximal humerus, wrist, rib
bone densitometry2
Bone Densitometry
  • Never round up figures
    • -1 is osteopenia, -0.99 is normal
    • -2.5 is osteoporosis, -2.49 is osteopenia
bone densitometry7
Bone Densitometry
  • T score is compared to reference population, 20-45 years, same sex, any race, any weight.
  • Z score is matched for age, sex, weight and ethnicity.
slide41
Two possible reasons for this lady’s Z score being

worse than the T score?

Obesity and race

slide42
The T score is based on a white, same sex, age 20-40population. The patient's BMD is compared to this population's BMD.A lower T score means that the patient BMD is low compared to this young, healthy normal weight population. The Z score compares the patient to an adjusted population, it adjustsfor age, weight, and ethnic background. The Z score can be lower than the T score for the patient, if the average patient in this population has a higher BMD than the average in the T score population. This can be seen in patients with higher weights, (which increases bone density), and in African American groups, (which show increased bone density).

If the patients comparison group has a generally higher bone density, then it is possible to have a poorer comparison to others of same age, than to younger comparisons in generally lower density group.

slide44
Black

as

Black

Black

as

White

slide45
Black

as

Black

>

Black

as

White

T same

Z up

<

bone densitometry weight gain loss and z
Bone DensitometryWeight gain/loss and Z
  • Weight gain(or loss) will not affect Z score comparison, since Z scores are weight matched, but should cause an increase(or decrease) in absolute BMD.
  • An increase in weight, pushes up the reference range, and therefore the Z score may seem reduced, and vice versa.

2.2lbs=1Kg

bone densitometry weight gain loss and t
Bone DensitometryWeight gain/loss and T
  • Weight gain (or loss) should cause an increase(or decrease) in absolute BMD.
  • Weight gain (or loss) will affect T score comparison, since reference range will not have changed.
  • Hence an increase in weight with a corresponding increase in bone density, will look like a good improvement in T score, but fracture risk is unchanged.
slide48
51F

90Kg

53F

51Kg

slide49
1.172

1.176

SD = 0.1 Both between -2 and -3 SD below mean for age

1Y, 16lb gain, 5% BMD loss

= significant increase in fracture risk

bone densitometry comparison with previous
Bone DensitometryComparison with previous
  • Are the studies comparable
  • Always compare like with like
    • Thornton L1-4
    • 4th and Lewis (previously L2-4)
  • Any intervening events
  • Cannot compare Hologic and Lunar
bone densitometry comparison with previous1
Bone DensitometryComparison with previous
  • David Sartoris’s previous studies that do not mention the region or levels measured, were standardized for L1-4 and the femoral neck.
  • He usually did not quote BMD.
  • Many previous studies were prior to the current database.
  • Use the percent young adult as a guide to percentage change.
bone densitometry comparison with previous2
Bone DensitometryComparison with previous
  • If over a period of time there is an increase in BMD in the lower lumbar spine and decrease in the upper lumbar spine, it is likely there is OA of the lower facet joints, and the upper lumbar spine is a truer reflection of useful BMD.
bone densitometry comparison with previous3
Bone DensitometryComparison with previous
  • Increase in BMD of the femoral neck can be due to calcar buttressing with OA of the hip.
bone densitometry comparison with previous4
Bone DensitometryComparison with previous
  • If you want to eyeball the % for a comparison, use the young adult % since the reference range will not change with age.
  • A static bone density is actually a good result over a significant period of time
  • If a test is 1% precise, then a change has to be greater than 2% to be significant
bone densitometry comparison with previous5
Bone DensitometryComparison with previous
  • If you would have expected the bone density to have fallen 4% in 2 years, and it is static, then this is a positive response to RX
bone densitometry comparison with previous6
Bone DensitometryComparison with previous
  • Generally Rx affects all levels equally.
  • OA does not.
bone mass in healthy children
Bone mass in healthy children

Radiology 1991;179:735-738

bone mass in healthy children1
Bone mass in healthy children
  • Increases with age, weight and pubertal Tanner stage.
  • Tanner stage and weight are best predictors of bone mass.
  • Age, sex, race, activity and diet are not good predictors, when weight and Tanner stage are controlled.

Radiology 1991;179:735-738

bone mass in healthy children2
Bone mass in healthy children
  • Make sure we have at least the age and weight of the child, if not the Tanner stage.

Radiology 1991;179:735-738

bmd in children and adolescents
BMD in children and adolescents

BMD in children and adolescents- Female- L2-4- Lunar

bmd in children and adolescents1
BMD in children and adolescents

BMD in children and adolescents- Male- L2-4- Lunar

slide69
5

63F

slide70
4

63F

slide71
3

63F

slide72
2

63F

report
Report
  • Because of the previous laminectomy at L4, which may also be affecting the reading on the inferior aspect of L3, the BMD is averaged at L1-2. Note is also made of mild decrease in the L4 vertebral height.

1

63F

slide74
New Case

3

35F White 242lbs 62in

slide75
2

35F White 242lbs 62in

report1
Report
  • Because of the patients weight, the T score may not fully represent the fracture risk, and note should be made that the Z score is 1.7 SD below age and weight matched.

1

35F White 242lbs 62in

slide77
New Case

2

OGI

39M

report2
Report
  • The very low bone density is compatible with the known diagnosis of osteogenesis imperfecta.

1

39M

slide80
3

Calcified bile

46 F

slide81
2

46 F Calcified bile

report3
Report
  • Although the calcified bile is seen on the DEXA scan, it is outside the measured region and will not affect the reading.

1

46 F Calcified bile

slide83
New Case

Black

2

47F

report4
Report
  • The Z score is worse than the T score at all levels because the the Z score is compared to weight and ethnicity and African American females naturally have a higher bone density than the standard Caucasian used for the T score, even at the age of 47.

1

African American 47F

slide85
New Case

2

49F 2Y8M gap Lx spine up, Fem neck down

report5
Report
  • A common cause for the bone density of the lumbar spine to increase whilst that of the femoral neck decreases over time is, the development of lower lumbar spine end plate sclerosis and facet osteophytes.

1

49F 2Y8M gap Lx spine up, Fem neck down

slide87
New Case

T

2

Sacral agenesis

49F

report6
Report
  • It is likely that only L1 represents close to true bone density and use of femoral neck measurements alone is recommended.

1

Sacral agenesis 49F

slide89
New Case

3

Dense R femoral neck

50F

slide90
2

50F dense R femoral neck

report7
Report
  • In view of the significant discrepancy between the right femoral neck and lumbar spine measurements , radiographs of the right hip/pelvis are recommended.

1

50F dense R femoral neck

slide92
New Case

2d earlier

2d later

3

51F

slide93
2

51F Barium in diverticulum from recent enema

report8
Report
  • It was noticed that the patient has had a recent barium study and that barium may therefore falsely elevate the bone density. A repeat study is therfore recommended.

1

51F Barium in diverticulum from recent enema

slide95
New Case

53F

51Kg

6 yr later, 8Kg wt loss

47F

59Kg

2

slide96
47F

59Kg

53F

51Kg

1

report9
Report
  • As the patient loses weight the T score worsens at a faster rate than the Z score because the reference range for the Z score also is lowered.
  • However with the loss of weight the fracture risk does not increase as much as the T score worsens.

1

6 yr later, 8Kg wt loss

slide99
2

60F OA

report10
Report
  • Because of lower lumbar spine degenerative changes the lumbar spine should not be included in the study.

1

60F OA

slide101
New Case

3

Rec. repeat

54M ESLD s/p trans

slide102
New Case

2

Rec. repeat

54M ESLD s/p trans

report11
Report
  • Only technical error could account for such a finding and therefore repeat study is recommended.

1

54M ESLD s/p trans

slide104
New Case

15m earlier

15m later

76F response to Rx

2

report12
Report
  • If all levels increase in bone density over time, it is likely a response to treatment.

1

76F response to Rx

slide106
New Case

85M Bil THR

3

report13
Report
  • When the lumbar spine and hips cannot be used we turn to the distal radius and use the ultradistal measurement.

1

85M Bil THR

slide109
New Case

4

DEXA 51F

slide110
3

DEXA 51F

slide111
2

DEXA 51F

report14
Report
  • Increase in lumbar spine bone density is due to syndesmophytes and ligament ossification.

1

Ank Spond DEXA 51F

report15
Report
  • Calcium anterior to the spine can increase apparent BMD.

1

DEXA pancreatic Cal 59M

report16
Report
  • If the patient does not wish to divulge their personal details, only T score and not Z score can be produced.

1

DEXA no personal data 50M

slide118
3

59F

report17
Report
  • Benign bone sclerosis such as Worth’s disease or Van Buchem’s, or a variant of osteopetrosis.
  • Recommend repeat DEXA to check for spurious result.

1

High bone density 8SD 59F

slide122
3

62F

slide123
MDP

2

62F

report18
Report
  • Benign sclerotic lesion L1
  • Levels may be incorrect.

1

report19
Report
  • When a vertebrae collapses, initially it will be of higher density.

1

DEXA L1 fracture 76F

slide130
1Y prior 2m prior

DEXA with islet cell met to L2 65F

report20
Report
  • Look out for vertebrae with a different and unaccountable bone density, either higher or lower.

1

DEXA with islet cell met to L2 65F

report21
Report
  • 5’2”, 182lbs

1

report22
Report

1

55F

report23
Report
  • Good response to Rx

1

bone densitometry depa
Bone DensitometryDEPA
  • Gd153
  • Accuracy similar to QCT
  • Less radiation than QCT
  • Measures cortical and trabecular
  • Less sensitive to early changes
  • Affected by aortic Ca2+
bone densitometry qct
Bone DensitometryQCT
  • Single energy 97% accurate
  • Dual energy not routinely available
  • 300mR
  • Fat content adversely affects accuracy
  • Difficult to reproduce positioning
  • Can only measure trabecular bone
  • 8X increase turnover of trabecular bone
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